Hi..
Thanks for the query..
As per your complain it seems that due to hitting with the edge of the stairs there has been
injury to the soft tissues and lump seems to be due to
hematoma formation and it occurs due to rupture of blood vessels and accumulation of blood in the soft tissues..
Hematoma is a harmless
tumor like mass formed due to spillage of blood from ruptured blood vessels leading to accumulation of blood into the soft tissues forming a lump..
At times the hematoma gets localized and encapsulated and forms a firm hard lump that can take a long time, say a few months to resolve, but it generally tend to resolve itself.
Pain is due to inflamed tissues only..
I would suggest you to do cool compresses over the area..
You can take anti inflammatory painkiller like
Ibuprofen..
Apply
Heparin gel as it will help in resolving the lump soon..
Elevate your leg while lying down and also limit exertion..
In case of no improvement in a week consult an Orthopedician and get evaluated..
Hope this helps..
Regards..